This invention is directed to plasticized polyamide monofilaments containing abrasive particles that are useful as bristles in brushes used for example for polishing a wide variety of materials.
Polyamides and other thermoplastic polymers have been used to form monofilaments containing an abrasive filler and the monofilaments have been used widely for bristles in brushes used for polishing metals and electronic parts. U.S. Pat. No. 3,522,342 issued Jul. 28, 1970 to Nungesser et al shows an apparatus and process for making such monofilaments. U.S. Pat. No. 4,507,361 issued Mar. 26, 1985 to Twilley et al shows low moisture absorption bristles of blends of polyamides and polyesters containing an abrasive filler. U.S. Pat. No. 4,585,464 issued Apr. 29, 1986 to Haylock et al shows low moisture absorption abrasive bristles of polybutylene terephthalate.
In the polishing of parts under dry conditions temperature resistance rather than moisture absorption is critical in maintaining stiffness of the bristles. When a polyamide such as Nylon 6,12 or Nylon 6,10 or blends of polyamides and polyesters are operated at temperatures of 220.degree. C. and above, they lose their stiffness and ability to cut materials at the elevated temperatures such as those that typically occur under dry brushing applications. If a monofilament of a polyamide that has a higher temperature resistance, such as Nylon 6,6 (polyhexamethylene adipamide), is used as the bristle for a brush, the bristles fracture at the base of the brush after only a short period of operation since these polyamides are relatively brittle and have a low degree of flexibility.
There is a need for a monofilament containing an abrasive material that can be used for bristles of brushes that operate effectively at relatively high temperatures under dry brushing and polishing conditions. The polyamide monofilaments of the present invention operate effectively under such conditions.